Buildings are responsible for 30 to 40% of the global energy demand. ³ Disregard for Egypt’s building context, location, and climate is the reason for undesirable building performance in this regard. Occupants’ needs can be often ignored, in terms of well-being and productivity. The primary energy demands of educational buildings are attributed to lighting and ventilation. Since building envelopes are the barrier between the internal and external environment, controlling natural lighting and ventilation would be ideal in order to apply sustainable design strategies to achieve the optimum levels of IEQ, comfort, well-being, health and productivity. With Egypt’s recent development and economic growth, the western aesthetic approach of fully glazed building envelopes has been mimicked in a misplaced environmental context and cultural background. It causes enormous energy demand accompanied by energy shortages. ⁴ This approach has added to the economic crisis. Thus, Egypt has urged stakeholders to use new technologies to reduce energy consumption. This paper aims to address the advantages of using SABEs in educational buildings using simulation-based comparative methodology, to compare between building performance with and without using SABEs. SABEs respond to the local environment and climatic challenges, to provide thermal comfort and natural daylight with the least energy consumption.

Climate change impact on Alexandria

Recently, coastal cities have been vulnerable due to their location; significant events of flooding, sea-level rise or unexpected weather patterns can drastically impact infrastructure, the construction of buildings, transportation networks, drainage systems, and communication networks. These drastic events will affect not only coastal cities but also coastal communities. More than 360 million inhabitants of coastal cities which are 10m above sea level are prone to natural catastrophes that threaten their lives, like storm surges and floods, due to climate change. ⁵

Alexandria is already facing the impacts of climate change and is expected to face serious challenges in the future. It is the second-largest city in Egypt. The population is in continuous increase; currently it is 5,449,817 and growing by 1.9% every year. The city of Alexandria has the largest harbor in Egypt. Alexandria has a moderate climate as a result of its location. The climate in Alexandria is classified as BWh by the Köppen-Geiger system, ⁶ with subtropical deserts, moderate winters with light rainfall and dry summers. ⁷ During the past few years, Alexandria has witnessed a decrease in temperature accompanied by rain during winter, and significant heat waves with a high percentage of humidity during summer. ⁸ The average annual temperature of Alexandria is 20.8 °C, a continuous increase as it was 14 °C in 2018. ⁷ The average yearly precipitation is 181 mm.

External climate and built environment

Since it is quite challenging to withhold climate change phenomena, ⁹ global efforts are now focused on developing sustainable methods and strategies to anticipate, assess, and control buildings’ performance under the foreseen consequences of climate change. ¹⁰ Buildings act as a climate modifier since they separate the indoor spaces from the external climate change events. Buildings and climate influence each other; they have a direct interrelationship. ¹¹ Buildings contribute to climate change due to their heavy energy consumption, which also affects the functionality of buildings. ^{12 , 13} Thus, the sustainable design of buildings is key in overcoming the consequences of climate change by responding to different climatic patterns.

Designing sustainable and resilient buildings has significant potential for greenhouse gases reduction. ¹⁴ Several factors, however, must be considered to achieve sustainability in the built environment, such as energy efficiency and thermal comfort. ¹⁵ Strategies for designing sustainable and resilient buildings can broadly be categorized as mitigation strategies and adaptation strategies ¹⁶ as shown in Figure 1. Mitigation strategies focus on preventing or reducing greenhouse gases to make the impact of climate change less severe. Adaptation strategies, on the other hand, focus on responding and adjusting to the current or the future impacts of climate change. Table 1 shows the difference between mitigation and adaptation strategies in terms of spatial scale, time and sector. Adaptation strategies are further classified into two categories: active and passive. ¹⁷ Active strategies encompass the efficiency of ventilation technologies and strategies like HVAC. On the other hand, passive responses focus on bio-climatic concepts, for example building orientation, insulation methods and natural ventilation. Passive strategies are used to attain thermal comfort within the interior environment by reducing thermal exchange between the interior and exterior environment. This paper focuses on the passive strategies of sustainable educational buildings to provide the optimum comfort for building users and reduce energy consumption.

Building performance: IEQ

Historically, IEQ did not receive much attention from designers or users than other building-related topics. ¹⁸ But recently, IEQ has been gaining more attention than ever; it is involved in building design, policymaking, and building regulations. However, IEQ itself is a contested topic due to the multidisciplinary interest in it. As a result, there are several competing definitions, further leading to misinterpretations of what is considered good IEQ for building users.

The objective concept of energy efficiency in combination with subjective ideas of well-being is vital to achieving sustainable buildings. Well-being, health and comfort are defined as perceptual and physical qualities that play a vital role in the everyday experience of architecture and in connecting indoor to outdoor spaces. ¹⁹ Users’ perception of indoor thermal comfort or discomfort depends on physiological and psychological reactions to the thermal characteristics of a space. ²⁰ Therefore, thermal characteristics are interweaved between tangible characteristics and the immaterial dimensions of the built environment. ²¹

The quality of life inside buildings is defined by the IEQ. ²² IEQ influences occupants’ comfort, health and productivity. ²³ However, IEQ is influenced by climatic conditions, occupants’ factors ²⁴ and different building-related factors. ²⁵ There are four main factors that tackle IEQ: indoor air quality (IAQ), thermal comfort, visual comfort, and acoustic comfort. ²⁶ This paper focuses on thermal comfort and visual comfort as follows:

Thermal comfort

Thermal comfort is one of the main parameters that control IEQ. Building occupants have to be thermally comfortable to be optimally productive. Thermal comfort depends on the occupant’s thermal adaptation, influenced by personal factors such as metabolic rate and clothing, and environmental parameters such as solar radiation, humidity, air velocity, and temperature. ²⁷ In the case of occupants’ exposure to a sense of thermal discomfort, this leads to increased energy consumption to achieve thermal comfort. Factors that influence thermal characteristics need to be considered during the design phase to achieve optimum thermal comfort. Making early decisions and considering these factors in the early design stage reduce energy consumption save money and time.

Visual comfort

Visual comfort plays a vital role in well-being and productivity, especially in educational buildings. ²⁸ Work productivity, performance and satisfaction are affected by visual comfort within workspaces. ²⁹ Lighting is a key factor affecting visual comfort, and physical and psychological health is affected by visual discomfort. For instance, insufficient light decreases the ability to see small details clearly. ^{30 , 31}

Visual comfort is an essential quality in educational buildings. Thus, a building’s sources of light (daylight and artificial light) should be considered during the architectural design phase to get a more holistic image ³² since it directly impacts well-being, productivity, and satisfaction. Window dimensions, geometry, and glazing control the amount of natural light inside spaces. Artificial light is as crucial as natural light to ensure visual comfort throughout the day. Natural light is important for creating better IEQ. However, glare can occur due to big windows that allow excessive light. Glare can cause significant visual and health problems. ³³ The acceptable range of glare is between 500-1500 cd/m ².

“Adaptivity/adaptation” is to understand, interpret, and interact due to alterations in the surrounding context and environment. The contextual and environmental changes are described by dynamism. Meanwhile, contemporary designs are often based on a set of static factors that hardly can adapt to dynamic changes, such as opening size and building structure. Environmental and climatic changes directly impact people’s daily lives and needs. Thus, the paradigm of designing a performance system has to change to attain a higher level of climatic response. Responding to dynamic environmental variables like solar patterns and wind variation in the static structure of conventional buildings creates disengagement between the building’s structure and its surrounding environment. High-performance dynamic adaptive systems must respond to climatic conditions; these systems offer better efficiency and IEQ than static systems. ³⁴ Table 2 shows the advantages and disadvantages of SABEs.

For instance, in educational buildings that depend on mechanical air conditioning, there is a gap between the building envelope and its role as an environmental moderator. It also causes insensitivity to the surrounding environment. Sustainable buildings can adapt to the surrounding environment and its changes and take advantage of it. A building envelope is a key component in making the building sustainable, and its material, geometry, thermo-physical and optical properties. ³⁵ The majority of existing envelopes are used for heating or cooling purposes, depending on the climate. Adaptive building envelopes improve building energy efficiency by actively changing their thermal and optical properties, using kinetic energy to respond to climatic changes. ³⁶

The high-performance adaptive design approach adopts a passive design strategy for building envelope, impacting a building’s energy performance and consumption. ³⁷ The application of smart materials in building envelopes plays an important role in creating a sustainable passive design that can cope with environmental changes and offer building users different forms of comfort. The hybrid of adaptive and smart building envelopes achieves the goal of creating a comfortable indoor environment, regardless of the unexpected patterns of weather, with the minimum energy consumption.

SABEs can respond to climatic changes and integrate daylighting, shading and natural ventilation as mentioned in Table 2, which decreases the energy consumed by building operations. ³⁴ The building envelope is a significant aesthetic element. It can motivate architects and designers to settle for high-performance envelopes that will attract stakeholders and clients due to the design flexibility in using different technologies and materials to create varied visual features. SABEs are described as envelopes that can change their properties as a response to the surrounding environment and climatic changes, as they control the different parameters of the building envelope. ³⁸ The changes can occur in various forms, such as introducing airflow or chemical change in a material—the SABE helps create a better indoor environment to boost well-being and achieve the optimum IEQ for building occupants.

The pre-study step of the methodology aims to identify the problems facing the existing design of the studied building (AAST Al-Alamein campus) due to climatic changes. This step is divided into three parts as follows.

Problem identification: existing building simulation

This part analyzes the building performance to identify the problems encountered by the building.

The energy simulations for this project are conducted using an energy simulation engine called OpenStudio 3.0.1 by NREL. ³⁹ The 3d modelling software Rhino 7.0 educational version ⁴⁰ is used along with the Grasshopper 1.0.0 tool ⁴¹ to perform a parametric analysis of the existing and proposed SABE solutions. Blender is a free software that can work with Grasshopper the same way as Rhino using the same Grasshopper script. Honeybee 1.1 ⁴² is a wrapper for OpenStudio that enables parametric energy simulation within Rhino as a plug-in. As shown in Figure 3, all the simulation results in the following section are produced via Honeybee. The simulation is a 3-step process to generate the results. 1.

Zoning and 3D modelling: a thermal model is created based on auto computer-aided design (CAD) drawings provided by the AAST to represent the existing building accurately. Zoning is an important step in the energy modelling process. It captures the real use cases of each room in the building; the energy consumption and comfort requirements in classrooms are different from those in a mechanical room. In addition to the zoning, details about the existing building envelope are also considered using the auto CAD drawing; the windows and atrium’s location, type and size are extracted.

4-Results: building simulations are used in the AAST Al-Alamein campus with a focus on three aspects as follows:

Indoor thermal comfort •

This component requires input like outdoor temperature, wind speed and mean radiant temperature.

The output of this component is thermal comfort percentage, operative temperature –summer and operative temperature- winter, and predicted mean value (PMV).

Daylight

This component requires input such as: •

Annual radiance: a list of annual radiance configuration files from the “Honeybee (HB) Annual Daylight” which includes predefined components such as weather file, test points for measuring daylight and the sun-up hours, while setting the complicated components as default.

The output of this component is useful daylight illuminance (UDI) and glare analysis; amongst other outputs, daylight autonomy (DA) and continuous daylight autonomy (cDA). DA and cDA are the previous version of the UDI method and provide no additional data. Hence, they are not considered in this study.

Energy usage •

Holidays: all holidays, including the weekends, summer and winter holidays, are identified.

The outputs of this component are a data tree with all of the building-wide energy balance terms; normalized energy balance is the one chosen as the normalized values make the energy consumption results comparable.

Solution identification: material selection

SABEs are claimed to be a solution for achieving optimum IEQ and reducing energy consumption. However, a SABE is a hybrid, incorporating smart materials in adaptive envelopes. There are different types of smart materials, each has a unique set of factors which are: •

Physical properties (response factors).

The factors of adaptation, location of the building and cost budget are the decision support tool for choosing the right smart material for the building envelope.

Solution identification: movement selection

The movement of the building envelope is another variable that is selected based on a set of factors as follows: •

Environmental factors (adaptation factors)

These factors are also part of the decision support tool to select the right movement of the building envelope.

The purpose of step two is to apply the identified solution (material and movement of SABEs) to assess the building performance by simulating indoor thermal comfort, daylight and energy usage. Comparing the existing building results and the proposed design serves to confirm or disprove the hypothesis that SABEs can enhance IEQ for occupants and reduce energy consumption. This step is divided into three parts as follows:

Proposed SABE design

The two results from the previous step, identifying the problems and solutions, are used to inform the design of the hypothetical SABE. Identifying the problem allows the proposed design to be specific to the site and its context, whereas identifying the solutions ensures that the SABE is suitable for the building theoretically and feasible practically.

Proposed building simulation

Simulations analyze the indoor thermal comfort, daylight and energy usage of the building with the proposed SABE design; to evaluate the performance of SABEs.

Comparison: existing vs proposed

Comparing the existing design results to the proposed building performance in terms of indoor thermal comfort, daylight and energy usage gives an idea of how effective the SABE is in addressing the problems identified in result 1A. Hence, ensuring that the decision support tool functions as intended.

Indoor thermal comfort

The indoor thermal comfort component analyzes the adaptive comfort for building users. Building occupants adapt themselves to the monthly mean temperature; occupants would feel comfortable if the building temperature is close to the monthly mean temperature, above 10 °C and below 33.5 °C.

Thermal comfort percentage

Thermal comfort percentage is the annual percentage of time during the building’s active occupancy that occupants feel thermal comfort. The comfort percentage is determined using ASHRAE-55, the adaptive comfort criteria and the metabolic rate for the occupants performing daily activities according to a schedule. The results of the simulation for the existing AAST Al-Alamein building indicate the following ⁴⁴ : •

The atrium of the building has the worst performance,

The atrium serves as a transitional space for circulation and special events; in comparison, students and teachers spend most of their active hours in classrooms and internal zones.

Operative temperature

Operative temperature is the calculated temperature of each grid point in the simulation model. The analysis period selected is for two key hours: the summer solstice (21st of June from 13:00 to 14:00) and the winter solstice (21st of December from 13:00 to 14:00). These hours are selected to present the shortest and longest days representing the highest and lowest operative temperature, respectively. •

The zones along the west and south of the buildings experience heat.

Predicted mean value (PMV)

PMV is the prediction index value of a group of occupants on their thermal sensation scale; the scale has seven points. Thermal equilibrium is achieved when the heat loss is equivalent to internal heat production. The heat balance is influenced by personal factors and environmental parameters, such as metabolic rate, clothing and airspeed, temperature. Personal factors are identified based on the material selection, load and schedule steps. Simulation runs calculating PMV during the summer solstice (21st of June from 13:00 to 14:00) and winter solstice (21st of December from 13:00 to 14:00). The result of the simulation shows the following: •

Building occupants feel slightly warm on the eastern side and feel hot closer to the southern and western windows of the building during the summer.

Daylight

Daylight analysis calculates the quantity and quality of daylight within indoor spaces. It analyzes the daylight factor- the ratio between the interior and exterior natural lighting illuminance level.

Useful daylight illuminance (UDI)

UDI is a metric of available daylight in a space, which corresponds to the percentage of occupied time when a target range of illuminances at a point is met by sunlight. Daylight illuminances are set to be desirable between the ranges of 300 to 3000 lux. ⁴³

The UDI low-value analysis shows the areas that need artificial lighting, approximately 70% of the whole building, as shown in Figure 4(a). On the other hand, The UDI high-value analysis shows the spaces that have natural daylight-as shown in Figure 4(b). However, some of them have a high intensity of natural sunlight that may cause discomfort to the building occupants.

The UDI simulation of the existing building design shows the following: •

The rooms facing the west, south and north sides of the buildings require no artificial lighting.

Glare analysis

Glare is visual discomfort caused by excessive and uncontrolled light. When direct light shines into the eyes, it is hard for the eyes to adjust to the sudden level change of illumination. Glare problems in educational buildings are significant and can cause occupants health problems. The glare analysis aims to visualize indoor spaces with glare problems. Four classrooms are analyzed to examine the glare situation to measure the glare occurrence in an internal space; the rooms were selected based on the location as shown in Figure 5 and Figure 6; to show the effect of glare on each side of the building; north, south, east and west. The acceptable glare is up to 1500 cd/m ².

As shown in Table 3, the maximum glare exposure to the four rooms is below 1500 cd/m ², within the acceptable range. Thus, glare is not one of the issues affecting the existing building performance and IEQ.

Energy usage

Energy usage analysis calculates the energy consumption of the building. The cooling demand is generated based on standard equipment load for the zone, and occupancy load is generated from the users occupying the zones. The major areas of energy consumption of buildings are heating, cooling, lighting.

Normalised energy balance

The energy demanded for heating and cooling is directly related to the external temperature. The energy needed for cooling begins consumption in March and increases gradually to reach the peak during July, which has the highest temperature, and stops by October. The energy required for heating begins consuming in November, gradually increasing until reaching the peak in January, which has the lowest temperature, and gradually decreases till April. •

Peak energy consumption comprises heating, cooling, lighting, and equipment demands.

The results show unusually high results for the atrium; therefore, the atrium results are not included. Upon further investigation into the results, it is determined that the tools used in this simulation are not appropriate to analyze complex building physics, such as convection in the atrium. To sum up, Table 4 shows the highlights of the existing building design challenges.

Material selection

The selection of smart materials used in building envelopes located in coastal cities is based on criteria of identifying material properties (as shown in Table 5), environmental conditions of the building context, cost and accessibility (as shown in Figure 7).

This paper focuses on SABEs in coastal cities and, in particular, Alexandria. Successful material selection is based on choosing a material which is produced within Egypt or proximity countries and which has the properties that can adapt to the local climate. This has the added advantage of reducing carbon dioxide emissions in procuring the materials, stimulating the local economy of the region and incentivizes designers and decision-makers to choose the specified materials.

Figure 7 shows that the clustering of smart materials manufactured within Egypt is shape memory polymer (SMP), shape memory alloy (SMA), and electro active polymer (EAP). However, color-changing materials and phase change material (PCM) may also be available due to Alexandria’s ease of access and proximity to these. Regarding cost, PCM, thermos bimetals and EAP are considered the cheapest, while SMA is regarded as the most expensive. Therefore, SMP, SMA, EAP are focused on. Their properties, advantages, disadvantage and morphology are identified as follows:

By considering different types of smart materials in terms of advantages, disadvantages, morphology and factors of adaptation as shown in Table 5, and cost of manufacturing and location of production as shown in Figure 7, the SMA nickel titanium is selected to be applied as the “smart” material in SABEs (see Table 6).

Movement selection

A decision support tool is created to select the right SABE design for the building based on factors of adaptation, as shown in Figure 8. Based on result 1A, sunlight and temperature are the main adaptation factors for the selected case study; rotational panels have been selected. There are different typologies of panels (as shown in Figure 9); vertical panels are preferred if the north, east and west elevations are exposed to the sun since they can block the sun relatively well. Egg-crate shading devices are usually used for non-south facing, high-rise buildings. However, horizontal panels are selected since results-1A show the thermal comfort and light issues are mainly concentrated on the south, east and west sides of the building. It also allows a field for the external view (as shown in Figure 9) which is important for occupants of educational buildings.

There are two types of external shading devices: fixed and movable. Movable shadings can adapt to variable environmental factors like sun path (solar radiation) and external air temperature. It can be mechanically dependent or made from smart materials. Horizontal, vertical or egg-crate are the basic designs of shading devices as shown in Figure 9. It is necessary during the design phase to measure the preferable solar penetration during summer. Horizontal shading is suitable for southern exposure to the sun. For low rise buildings, south elevations can be shaded using roof overhangs. Horizontal panels and horizontal louvres are considered the most aesthetically pleasing solution for buildings that require good view access for outdoor spaces, like hospitals, residential and educational buildings.

SABE design

As a result of identifying the problems facing the existing building design (result 1A) and identifying potential solutions (result 1B), the SABE is proposed ( Figure 10).

The SABE consists of horizontal panels, static ones covering external walls (to add additional insulation to the western and southern sides of the building and aesthetically blend the window panels to the rest of the envelope) and dynamic ones covering windows. The panels are made of SMA (nickel titanium) supported by structure frames. The panels respond to solar radiation and temperature; they can respond automatically in two movements, primary and secondary, as shown in Figure 11. The horizontal panels vertically divided with the dimensions x*y are 0.30*0.20 m, to get better articulation of the panels. The actuators and sensors control the primary movements of the dynamic panels on the building envelope (open/closed movement). At the same time, the finer movement among individual panels is the properties of SABEs responding to environmental changes, as shown in Figure 12.

A SABE has two movements, primary and secondary, as shown in Figure 11. The primary movement is controlled by actuators and sensors on the building envelope that react at a larger time interval. The secondary movement controls the fine adjustments between the larger time intervals through a SABE’s smart properties. The actuators and sensors can also supplement the secondary movement during times with low solar radiation due to low thermal conductivity of SMA.

Proposed building simulation: results comparison

Building simulation runs again after applying SABEs to compare the difference between the existing building performance and the proposed SABE design in terms of indoor thermal comfort, daylight and energy usage as follows:

Thermal comfort percentage

The results vary from 0-100% and are colored from red to blue. Red regions imply that occupants in these zones are least comfortable, and the blue zones imply most comfort. It must be noted that the comfort percentage includes both heat and cold sensation. Hence, extreme hot and cold zones are both colored in red.

Thermal comfort percentage has significantly increased with the proposed SABE design to 40% of comfortability in rooms with external windows on the north, west, south and east sides, as shown in Figure 13. The percentage of time when the atrium is comfortable has also increased from 0 to 20%. The number of rooms that are 30% thermally comfortable and more has increased from 13 rooms to 57 rooms, as shown in Figure 14.

Operative temperature

The analysis grid is colored with its operative temperature in Celsius using a blue-yellow-red gradient color scheme. Blue is the lowest temperature, and red is the highest temperature. It must be noted that the range of values is different. The atrium is excluded from the analysis as previously mentioned, as it is a transitional space for circulation.

There is an extreme variation between the minimum and maximum temperature (24 °C). This intense heat is focused on the western window, and it is essential to address it. Though the hot spots are more prominent, the minimum and maximum temperature variations are not extreme (16 °C).

The operative temperature of the building during the winter solstice (21st of December between 1-2 pm), as shown in Figure 15, has a slight increase on the north and east sides by 1 degree. However, the temperature of the rooms on the south and west side of the building has dropped to 20-21 °C. The rooms overlooking the atrium have decreased by 2 degrees, reaching a range of 23.9 to 25.8 °C.

By comparing the existing building design and the SABE design, the number of rooms with an operative temperature of 26 °C has increased from 35 rooms to 48 rooms, as shown in Figure 17a, and the amount with temperatures of 28 °C have decreased from eight to three rooms. During winter, the operative temperature dropped in most rooms, as most rooms’ (20 rooms) temperature is 20 °C, as shown in Figure 17b.

Daylight: UDI

SABEs have a minor impact on the UDI of the rooms located on the north, east and north side of the building, as shown in Figure 21. However, UDI degraded in rooms located on the west side of the building, requiring more artificial light increasing electrical energy usage.

The number of rooms with UDI values of zero and 80 has increased from 25 to 28 rooms and from 7 to 11 rooms, respectively, as shown in Figure 22. The number of rooms with a UDI value of 60 has significantly decreased from 14 to 9 rooms.

Energy usage: normalized energy balance

Energy usage has significantly decreased, as shown in Table 7. The total peak energy consumed has reduced by 7.62% during summer and 5.42% in winter. Heating demand during winter has decreased by 5.52%, and cooling demand during summer reduced by 5.84%. Lighting demand has reduced during summer and winter by 7.04% and 4.67%, respectively. A fraction of energy is used for other mechanical purposes throughout the year.

Indoor thermal comfort, daylight and energy consumption is improved by using SABEs. The peak end-use energy for heating, cooling and lighting is calculated as follows:

End-use energy = energy-use intensity (see Table 8)/coefficient of performance (CoP).

CoP of heating ranges between 2.0-4.0, CoP of cooling ranges between 2.3-3.5.

CoP of heating is assumed as 4 and cooling as 3.5.

The guidelines are sorted into two scales, internationally and locally, to improve educational buildings located in coastal cities. The following guidelines are for the international scale: •

Analyze climatic zone and understanding climatic challenges.

A set of recommendations are given for educational buildings located in Alexandria, Egypt, the local scale: •

Three types of smart materials that are recommended to be used, which are SMP, SMA and EAP.

Mendeley data: SABE Simulation. http://doi.org/10.17632/b9db42k7pm.1 ⁴⁴

This project contains the following underlying data: •

annual_daylight_inputs.json (The required inputs for the Honeybee annual daylight simulation).

Mendeley data: SABE Simulation. http://doi.org/10.17632/b9db42k7pm.1 ⁴⁴

This project contains the following extended data: •

iso_01.jpg (Exploded diagram of SABE design).

Data are available under the terms of the Creative Commons Attribution 4.0 International license (CC-BY 4.0).